1. Field
The following description relates to a method and an apparatus of measuring a biosignal, a photoplethysmographic measurement apparatus and method, and a method of acquiring a photoplethysmogram (PPG).
2. Description of Related Art
With the widespread use of personalized electronic devices such as smartphones and tablet computers, various efforts have been directed to utilizing biosignals that are sequentially or continually measured from an individual in the fields of healthcare, personal well-being, entertainment and human-machine interface. A heart rate of a person may provide a variety of information about the health condition of the person, such as, for example, stress and exercise. A person's heartbeat may be relatively simply detected, and detecting two or more heartbeats may allow calculation of the heart rate. Likewise, a respiratory rate of a person provides a variety of information about the health condition of a person. Thus, a person's heart rate and respiratory rate are applied as preferred biosignals in various areas. A heart rate may be measured by many different methods. Photoplethysmography is a technique widely used along with electrocardiography in measuring the heart rate of a person. In contrast to electrocardiography, photoplethysmography may be applied to readily detect a heartbeat at terminal appendages, for example, a wrist, and a fingertip, and provide a photophlethysmogram (PPG) indicating the heart rate of a person. Photoplethysmography may refer to a method of exciting a light source beneath a layer of skin, measuring light reflected from a skin tissue or transmitted through a skin tissue, and generating a PPG of blood penetrating the skin tissue. Thus, a light source and a light receiving sensor may be considered the constituent elements of a device configured to generate a PPG In an example, an implementation of a light source may be omitted, and ambient light may be utilized. However, a signal may be greatly affected by changes in the ambient light; thus, use of the ambient light may be difficult in various environments. In a biosignal measuring environment in which a personalized electronic device and a wearable device are utilized, the weight and volume of a system may need to be minimized. Further, it is desirable to reduce the power consumption to provide a low-power system. Thus, among constituent elements to be used to implement a photoplethysmographic measurement, a device that may reduce the lack of reliability of ambient light while saving a driving power of the light source may be needed.